package com.hmdp.service.impl;

import cn.hutool.core.swing.ScreenUtil;
import cn.hutool.core.util.BooleanUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSONObject;
import cn.hutool.json.JSONUtil;
import com.hmdp.dto.Result;
import com.hmdp.entity.Shop;
import com.hmdp.mapper.ShopMapper;
import com.hmdp.service.IShopService;
import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
import com.hmdp.utils.CacheClient;
import com.hmdp.utils.RedisData;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;

import javax.annotation.Resource;

import java.time.Duration;
import java.time.LocalDateTime;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;

import static com.hmdp.utils.RedisConstants.*;

/**
 * <p>
 *  服务实现类
 * </p>
 *

 * @since 2021-12-22
 */
@Service
public class ShopServiceImpl extends ServiceImpl<ShopMapper, Shop> implements IShopService {
    @Resource
    private StringRedisTemplate stringRedisTemplate;
    @Resource
    private CacheClient cacheClient;
    //利用redis查询商户信息
    @Override
    public Result queryById(Long id) {
        //缓存穿透
//        return Result.ok(queryWithPassThrough(id));
//        Shop shop=cacheClient.queryWithPassThrough(CACHE_SHOP_KEY,id,Shop.class,this::getById,CACHE_SHOP_TTL,TimeUnit.MINUTES);
        //缓存击穿
        //使用互斥锁解决缓存击穿
      //  Shop shop=queryWithPLogicalExpire(id);
        Shop shop=cacheClient.queryWithLogicalExpire(CACHE_SHOP_KEY,id,Shop.class,this::getById,CACHE_SHOP_TTL,TimeUnit.MINUTES);
        if(shop==null) {
            return Result.fail("店铺不存在");
        }
        return Result.ok(shop);
        //使用逻辑过期解决缓存击穿


    }
    public Shop queryWithMutex(Long id) {
        String key = CACHE_SHOP_KEY + id;
        //1.从Redis查询商户缓存
        String shopJson = stringRedisTemplate.opsForValue().get(key);
        if (StrUtil.isNotBlank(shopJson)) {
            //3.存在则直接返回
            return JSONUtil.toBean(shopJson, Shop.class);
        }
        //判断命中是否为空值
        //3.命中判断是否为空值，不为空直接返回，为空返回null;

        if (shopJson != null) {
            return null;
        }


        //4.未命中获取锁
        String lockKey = LOCK_SHOP_KEY + id;
        Shop shop = null;
        try {
            boolean isLock = tryLock(lockKey);
            //5.判断是否获取锁成功
            if (!isLock) {
                //9.获取锁失败，休眠重试
                Thread.sleep(50);
                //10.重试
                return queryWithMutex(id);
            }
            //6.获取锁成功，查询数据库
            shop = getById(id);
            //模拟高并发时的重建延迟
            Thread.sleep(200);
            //7.不存在，将空值写入redis
            if (shop == null) {
                stringRedisTemplate.opsForValue().set(key, "", CACHE_NULL_TTL, TimeUnit.MINUTES);
                return null;
            }
            //7.写入redis
            stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(shop), CACHE_SHOP_TTL, TimeUnit.MINUTES);
            //8.释放锁

        } catch (InterruptedException e) {
            throw new RuntimeException(e);
        } finally {
            unLock(lockKey);
        }
        //7.返回
        return shop;


    }


//定义一个线程池
private static final ExecutorService CACHE_REBUILD_EXECUTOR = Executors.newFixedThreadPool(10);

public void saveShop2Redis(Long id, Long expireSeconds) {
        //1.查询店铺数据
        Shop shop = getById(id);
        //模拟重建延迟
    try {
        Thread.sleep(200);
    } catch (InterruptedException e) {
        throw new RuntimeException(e);
    }
    //2.封装逻辑过期时间
    RedisData redisData = new RedisData();
    redisData.setData(shop);
    redisData.setExpireTime(LocalDateTime.now().plus(Duration.ofMinutes(expireSeconds)));

       //3.写入redis
    stringRedisTemplate.opsForValue().set(CACHE_SHOP_KEY + id, JSONUtil.toJsonStr(redisData));
    }
//逻辑过期解决缓存击穿
    public Shop queryWithPLogicalExpire(Long id) {

        String key = CACHE_SHOP_KEY + id;
        //1.从Redis查询商户缓存
        String shopJson = stringRedisTemplate.opsForValue().get(key);
        //2.判断是否存在
        if(StrUtil.isBlank(shopJson)) {
            //3.不存在则直接返回空
            return   null;
        }
        //4.命中，需要把json反序列化为对象
        RedisData redisData = JSONUtil.toBean(shopJson, RedisData.class);
        JSONObject data=(JSONObject) redisData.getData();
        Shop shop = JSONUtil.toBean(data, Shop.class);
        LocalDateTime expireTime = redisData.getExpireTime();
        //5.判断是否过期
        if(expireTime.isAfter(LocalDateTime.now())) {
            //5.1未过期，直接返回店铺信息
            return shop;
        }

        //5.2已过期，需要缓存重建

        //6.缓存重建
        //6.1获取互斥锁
        String lockKey = LOCK_SHOP_KEY + id;
        boolean isLock = tryLock(lockKey);
        //6.2判断锁是否获取成功
        if(isLock){
            //6.3获取锁成功，开启独立线程实习缓存重建
            CACHE_REBUILD_EXECUTOR.submit(()->{
                try {
                    //重建缓存
                    this.saveShop2Redis(id, 20L);
                } catch (Exception e) {
                    throw new RuntimeException(e);
                }finally {
                    //释放锁
                    unLock(lockKey);
                }

            });
        }

        //6.4返回过期商铺信息
        return shop;



    }
public Shop queryWithPassThrough(Long id) {

        String key = CACHE_SHOP_KEY + id;
        //1.从Redis查询商户缓存
        String shopJson = stringRedisTemplate.opsForValue().get(key);
        //2.判断是否存在
        if(StrUtil.isNotBlank(shopJson)) {
            //3.存在则直接返回
            JSONUtil.toBean(shopJson, Shop.class);
            return   JSONUtil.toBean(shopJson, Shop.class);
        }
        //判断命中是否为空值
        if(shopJson!=null) {
            return null;
        }
        //4.不存在则根据id查询数据库
        Shop shop= getById(id);
        //模拟高并发时的重建延迟

        //5.不存在，将空值写入redis
        //返回错误信息
        if(shop==null) {
            stringRedisTemplate.opsForValue().set(key,"",CACHE_NULL_TTL, TimeUnit.MINUTES);
            return null;
        }

        //6.存在，写入redis
        stringRedisTemplate.opsForValue().set(key,JSONUtil.toJsonStr(shop),CACHE_SHOP_TTL, TimeUnit.MINUTES);

        //7.返回
        return shop;
    }

private boolean tryLock(String key) {
    Boolean flag = stringRedisTemplate.opsForValue().setIfAbsent(key, "1", LOCK_SHOP_TTL, TimeUnit.SECONDS);
    return BooleanUtil.isTrue(flag);

}
private void unLock (String key){
        stringRedisTemplate.delete(key);
}
    @Override
    @Transactional
    public Result update(Shop shop) {
        Long id = shop.getId();
        //判断id是否存在
        if(id==null) {return Result.fail("id不能为空");    }
        //1.更新数据库
        updateById(shop);
        //2.删除缓存
        stringRedisTemplate.delete(CACHE_SHOP_KEY +id);

        return Result.ok();
    }
}
